This invention relates to providing supplemental thermal energy to vehicles having living areas, and more particularly to providing supplemental heat to over-the-road and marine craft having rooms and domestic water to be heated.
Vehicles of many types have been used to provide temporary living or working quarters. These include self-propelled over-the-road vehicles, such as so-called recreational vehicles powered by internal combustion engines. Also, self-propelled vans have been used as mobile work spaces, such as for providing medical services at remote or movable locations in a city. Other self-propelled vehicles include boats in which internal combustion engines provide the primary power source. Other non-self-propelled vehicles, such as trailers, have been used to provide shelter for temporary living, such as for vacation or recreation. Also, trailers are used to provide space for performing work, such as at construction sites or performing atmospheric sensing at remote locations.
All of these vehicles are characterized by the need to provide heated space, in the form of at least one room. In general, many separate rooms or work areas are provided. Also, sanitary facilities are provided in such vehicles, and include plumbing fixtures such as sinks, showers, and toilets that use domestic water, especially heated water.
The term xe2x80x9cvehiclexe2x80x9d is used herein to refer to all types of vehicles, whether or not self-propelled and whether an over-the-road or water vehicle, so long as there is a space to be heated in the vehicle and/or a requirement that heated domestic water be available for use. The term xe2x80x9cvehiclexe2x80x9d may also include the above type of vehicle that is also provided with a main power source, such as an internal combustion engine, that has a primary function of propelling the vehicle on land or water. Customarily, those main power sources are heated when not in operation, so that they will start readily when the vehicle is to be moved.
The main power source of such vehicle is turned off when the vehicle arrives at the destination, and reliance is placed on a supplemental source of thermal energy. Such supplemental thermal energy sources include diesel-fired and gasoline-fired burners, such as those disclosed in U.S. Pat. Nos. 2,726,042 and 3,877,639.
An improved heating system for a recreational vehicle is described in U.S. Pat. Nos. 5,025,985 and 5,067,652, both of which are incorporated herein by reference in their entirety. However, improvements are desirable. For example, it would advantageous if the heating system were compact, so as not to take up more valuable space in a vehicle than is necessary. It would be advantageous if the heating system included an efficient control system. It would be advantageous if the heating system could provide space heating and hot water heating, as well as optional engine heating if desired.
In accordance with the present invention, a heating system is provided which includes a heating medium and a first heat transfer device located within said heating medium capable of heating a fluid flowing through the first heat transfer device. Operatively connected to the input side of the first heat transfer device is a first temperature sensor. This first temperature sensor is located outside of a tank which contains the heating medium. When the fluid to be heated, such as cold water to be heated for domestic hot water use, flows through the first heat transfer device, the first temperature sensor will register a relatively low temperature because the fluid flowing past it is cold. When the first heat transfer device is not in use, the first temperature sensor will register a higher temperature, due to conduction of heat from within the tank to the nearby location of the first temperature sensor. Preferably, a second temperature sensor is also provided which measures the temperature of the heating medium within the tank. Preferably the second temperature sensor is in direct fluid contact with the heating medium within the heating tank. The heating medium can also be pumped out of the tank in order to provide heat for desired purposes, such as space heating purposes. Alternatively, a separate heat transfer fluid can be employed which passes through a second heat transfer device within the tank to obtain heat from the heating medium and to circulate it for desired purposes, such as space heating purposes. A heat source, preferably a diesel fuel-burning heat source is provided to heat the heating medium. Preferably, a tank agitation device is also provided in order to provide efficient heat transfer to the heat transfer device or devices located within the tank.
Preferably the heat tank is more compact than those provided in prior art devices such as those disclosed in U.S. Pat. Nos. 5,025,985 and 5,067,652. Preferably the tank is a rectangular box or cube as opposed to a sphere or cylinder. In this way the tank can be more efficiently placed within a vehicle and uses the space more efficiently. Preferably the tank is about one third the size of prior art tanks. Preferably the heating system uses lower temperatures and pressures than those found in prior art tanks. Preferably, an optional heating loop is provided for engine preheating. This heating loop can use the heat transfer medium directly or use a separate heat transfer medium and a heat transfer device within the heating tank. In FIGS. 4 and 5, a heat transfer device is illustrated for heating water for domestic hot water use and the heat transfer medium is used directly for space heating. The optional engine heater is also illustrated.
In accordance with the method of the present invention, a heating fluid is heated within a tank. A first heat transfer device is provided within the tank in order to heat a fluid such as water for domestic hot water use. A first temperature sensor is provided external to the tank, but near the tank on the inlet side of the first heat transfer device. A cool fluid such as cold water flows past this first temperature sensor into the heat transfer device located within the heating medium. Heat is transferred from the heating medium to the fluid flowing through the first heat transfer device which exits and can be employed, e.g., as domestic hot water within a recreational vehicle. The heating medium can also be circulated through the vehicle and in particular through heat transfer devices located within the vehicle, for space heating purposes, as illustrated in FIGS. 1, 2 and 3. It can also be employed for engine preheating. Alternatively, second and/or third heat transfer devices can be located within the heating medium to provide the heat to a circulating fluid which is employed for space heating purposes and/or engine preheating purposes. A second temperature sensor is provided to determine the temperature of the heating medium within the tank. Preferably this second temperature sensor is in fluid contact with the heating medium. Preferably a control system is provided, including temperature sensors which are preferably solid state, although mechanical controls and/or sensors can be used. The control system can be employed to selectively disable parts of the heating system.